Angry Birds is a puzzle video game developed by Finland-based Rovio Mobile. Inspired primarily by a sketch of stylized wingless birds, the game was first released for Apple's iOS in December 2009. Since that time, over 12 million copies of the game have been purchased from Apple's App Store, which has prompted the company to design versions for other touchscreen-based smartphones, such as those using the Android operating system, among others.

In the game, players use a slingshot to launch birds at pigs stationed on or within various structures, with the intent of destroying all the pigs on the playfield. As players advance through the game, new birds appear, some with special abilities that can be activated by the player. Rovio Mobile has supported Angry Birds with numerous free updates that add additional game content, and the company has even released stand-alone holiday and promotional versions of the game.

Angry Birds has been praised for its successful combination of addictive gameplay, comical style, and low price. Its popularity led to versions of Angry Birds being created for personal computers and gaming consoles, a market for merchandise featuring its characters and even long-term plans for a feature film or television series. With a combined 200 million downloads across all platforms and including both regular and special editions, the game has been called "one of the most mainstream games out right now", "one of the great runaway hits of 2010", and "the largest mobile app success the world has seen so far".

Angry Birds Seasons
In October 2010, Rovio released a special Halloween edition of the game. Angry Birds Halloween, exclusive to Apple iOS at the time and a separate application from the main game, included new levels with Halloween-themed music and graphics. In December 2010, Rovio released Angry Birds Seasons to iOS, Android and Symbian^3 devices. Seasons introduced 25 Christmas-themed levels, one for each day leading to the holiday, similar to an Advent calendar. All versions include the previously-exclusive Halloween levels and are offered as separate, stand-alone paid applications, with the exception of the free, ad-supported Android version; Angry Birds Halloween users on iOS received the Seasons levels as a free upgrade. The Halloween version was given the episode title "Trick or Treat", while the Christmas episode was entitled "Season's Greedings". In February 2011, Rovio released a new Valentine's Day update to Angry Birds Seasons, entitled "Hogs and Kisses", complete with new themed levels and graphics, as well as the option to send Angry Birds-themed Valentine's Day messages through Facebook. In March 2011, Rovio released a new St. Patrick's Day update, entitled "Go Green, Get Lucky", followed by an Easter update, entitled "Easter Eggs", in April 2011.

Angry Birds Rio
Angry Birds Rio, a stand-alone edition tying into the release of the 20th Century Fox animated film Rio, was launched for iOS, Android and Mac OS X in March 2011. In this version, the Angry Birds characters appear in Rio de Janeiro and interact with characters from the film. Angry Birds Rio initially includes two chapters, each with 30 levels; the Angry Birds rescue caged exotic birds in the first chapter and attack evil marmosets in the second and third chapters. The game also includes new hidden items and planned level updates in May, July, October and November 2011. The reception of Angry Birds Rio has been positive, with Ryan Rigney of GamePro saying the iOS version "boasts some notable improvements on its predecessors" and Levi Buchanan of IGN, in his review of the Android version, calling the game "a smart, snappy new chapter for the series". Since release, Angry Birds Rio has been downloaded more than 10 million times. The first planned update, a new chapter called Beach Volley, was released in May 2011 and included 30 new game levels.

Angry Birds Magic
A special version of the game, called Angry Birds Magic, will be developed exclusively for Nokia's NFC-enabled Symbian devices. This version of the game will include functionality that will unlock game levels upon contact with another NFC-enabled phone running the game. A free version of Angry Birds Magic will come preinstalled with all NFC Symbian devices to be sold in 2011, starting with the Nokia C7.